Omicron Hospitalization Risk Is Far Below Delta’s in Two Studies

Infection with the omicron variant is far less likely to land patients in the hospital than cases involving the delta strain.

The highly-mutated omicron variant appears less likely to land patients in the hospital with Covid-19 than the delta strain, according to preliminary data from a trio of studies. 

Researchers in Scotland found omicron was associated with a two-thirds lower risk of hospitalization compared to the earlier variant, though it was 10 times more likely than delta to infect people who’d already had Covid. An Imperial College London team working with a larger data set found that people with omicron were almost half as likely to need an overnight hospital stay.

The fresh data add to a study showing South Africans were 70% less likely to develop severe disease and 80% less likely to be hospitalized if they contract the new variant. The growing body of research provides preliminary reassurance that the omicron wave that’s inundating many parts of the world and sparking new records may be comparatively less dangerous than delta, at least in areas with high levels of pre-existing immunity. 

Record Cases

The highly contagious new strain could still overwhelm health-care systems as infections soar globally, the researchers said. Daily Covid cases in the U.K. surged above 100,000 Wednesday, the country’s highest single-day tally yet.

“It’s important that we don’t get ahead of ourselves,” said Jim McMenamin, national Covid-19 incident director for Public Health Scotland, which conducted the Scottish study with the University of Edinburgh and the University of Strathclyde. “A smaller proportion of a greater number of cases requiring treatment might still mean a substantial number of people that may experience severe Covid.” 

Omicron Hospitalization Risk Is Far Below Delta’s in Two Studies

Anthony Fauci, who serves as the top medical adviser to U.S. President Joe Biden, echoed those comments. While the Scotland study “appears to validate and verify” the data from South Africa, he warned that U.S. demographics may lead to different outcomes, and that the total caseload might eliminate any benefits from lower severity.

“Even if you have a diminution in severity, if you have a much larger number of individual cases, the fact that you have so many more cases might actually obviate the effect of it being less severe,” Fauci said at a briefing.

Booster doses offer greater protection against delta, and a third shot also offers substantial help in averting symptomatic infections caused by omicron, the Scottish team found. 

Rising infection rates in other parts of the world haven’t yet translated into overwhelmed hospitals. Australia’s most-populous state is hitting record highs as omicron became the dominant strain, with a 52% day-over-day increase in cases, though fewer than 50 people are in intensive care. 

Public health leaders cautioned that other factors, such as higher numbers of people who are vaccinated or have previously had Covid, may complicate comparisons with previous points in the pandemic. The Scottish study also included few people over 60. 

Two Doses

“When we measure severity of omicron, we are measuring it as South Africa did, in a very immune population,” said Neil Ferguson, a professor at Imperial, who helped lead the English study. After two doses of the Pfizer Inc.-BioNTech SE vaccine, the risk of hospitalization from omicron is probably about the same as the risk from delta, he said -- perhaps reflecting the fact that the new variant, though potentially somewhat less severe, is better at eluding the vaccine in people who haven’t had a booster. 

The English and Scottish studies had different follow-up times, meaning that the results may change as people’s illnesses progress, said Penny Ward, a visiting professor in pharmaceutical medicine at King’s College London. “It remains important for all of us to take reasonable care, test, test, test and get our boosters as soon as possible.” 

©2021 Bloomberg L.P.